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Mars I - Microarchitectures - Phytium
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Mars I µarch
General Info
Arch TypeCPU
Process28 nm
Core Configs64
TypeSuperscalar, Pipelined
Reg RenamingYes

Mars I is the first many-core ARM SoC microarchitecture designed by Phytium Technology for the Chinese server market.

Process technology[edit]

Mars I is designed for TSMC's 28 nm process.


This list is incomplete; you can help by expanding it.

Block diagram[edit]

Entire SoC[edit]

mars ii soc block diagram.svg


mars ii panel block diagram.svg


Main article: Xiaomi Core

See Xiaomi Core.


Panel Architecture[edit]

xiaomi panel-based data affinity architecture.png

Phytium organizes their processors using a grid-layout they call Panels they call Panel-based data affinity architecture. Each panel consists of 8 independent ARMv8-compatible cores. Phytium "Mars" processor consists of 8 such panels for a total of 64 cores. Panels are interconnected with a 2-dimensional mesh network-on-a-chip level 2 cache with 4 MiB per panel for a total of 32 MiB.

In addition to the main die, Mars uses an additional Cache & Memory chips (CMC) auxiliary chips. "Mars" uses 8 such chips connected to the main die providing 16 MiB of level 3 cache for a total of 128 MiB as well as 8 dual-channel DDR3-1600 memory controllers for a total maximum bandwidth of 204 GiB/s. Mars also provides two 16-lane PCIe 3.0 interfaces. The chips incorporates ECC and parity protection on all caches, tags, and TLBs.


Each Panel consists of 8 cores - each ARMv8-compatible, supporting AArch32 and AArch64 modes, Exception Levels EL0-EL3, as well as ASIMD-128 operations. Each core has its own inclusive L1 cache and a shared L2 cache (4 MiB per panel). Each panel contains two Directory Control Units (DCU) which are in charge of maintaining directory-based cache coherency and one routing cell for managing the inter-panel communication.

On TSMC's 28 nm process, a panel is 6,000 µm x 10,600 µm (63.6 mm²).

xiaomi panel.png   xiaomi panel die (28nm).png

Cache & Memory Chip (CMC)[edit]

xiaomi cmc.png

The solve the complexity involved in having more than eight memory controllers on a chip, Xiaomi uses a coupled auxiliary Cache & Memory Chip (CMC) to scale the bandwidth with computing power. In the case of Phytium "Mars" chip which contains 64 cores on 8 panels, eight CMC chips are used which provides 16 DDR3 controllers (8x2) along with 16 MiB of data L3 cache and 2 MiB of data ECC. Phytium proprietary interface is used between the processor and the CMC chip.

xiaomi latency.png
Memory access Latency(ns)
Local L1 cache hit ~2
Local L2 cache hit ~8
Affinitive L2 cache hit ~20
Affinitive L3 cache hit ~36
Affinitive DDR access ~70
  • Panel & NoC operates @ 2 GHz
  • CMC operates @ 1.5 GHz

Interconnects & Hawk[edit]

Hawk is Pythium cache coherence protocol which implements a distributed directory-based global cache coherency across all the panels. Hawk is a MOESI-like package-based protocol. The network has a node on each panel called a Directory Control Unit (DCU) which is responsible for interfacing between the L2 caches in each panel to the CMCs (see § Panel Architecture). Phytium noted that it's optimized for exclusive atomic accesses.

Xiaomi implements a 2D concentrated mesh architecture on-die connecting each of the panels. Phytium "Mars" chip contains 8 panels which are organized in two rows of four panels each. Switching is relatively low latency with 3 cycles per hop. On average, packets will have around 9 cycles latency from any other panel. This network results in a bandwidth of 384 GiB/s each cell.

xiaomi 2d network.png
Destination Latency
0 3
1 6
2 9
3 12
4 15
5 12
6 9
7 6
Average 9



  • Mars is fabricated on TSMC's 28 nm process
  • 10 metal layers
  • 4,800,000,000 transistors
    • ~180 million instances
  • 639.576 mm² die size
    • 25.38 mm x 25.2 mm
  • FCBGA Package
    • ~3000 pins
  • 0.9 VCORE, 1.8 VIO
  • 2 GHz, 120 W
xiaomi floor plan.png

All Mars I Processors[edit]

 List of Mars I-based Processors
FT-2000/6420176432 MiB
32,768 KiB
33,554,432 B
0.0313 GiB
2 GHz
2,000 MHz
2,000,000 kHz
120 W
120,000 mW
0.161 hp
0.12 kW
Count: 1


  • Phytium, IEEE Hot Chips 27 Symposium (HCS) 2015.
codenameMars I +
core count64 +
designerPhytium +
first launched2017 +
full page namephytium/microarchitectures/mars i +
instance ofmicroarchitecture +
instruction set architectureARMv8 +
manufacturerTSMC +
microarchitecture typeCPU +
nameMars I +
process28 nm (0.028 μm, 2.8e-5 mm) +